Human Anatomy, First Edition McKinley & O'Loughlin Chapter 6 Lecture Outline: Cartilage and Bone Connective Tissue

Skeletal System Composed of dynamic living tissues. Interacts with all of the other organ systems . Continually rebuilds and remodels itself. Includes the bones of the skeleton as well as cartilage, ligaments, and other connective tissues that stabilize or connect the bones. Supports our weight. Interacts with muscles to produce movements. Permits us to sit, stand, walk, and run.

3 Major Functions of Cartilage Supporting soft tissues. Providing a gliding surface at articulations (joints), where two bones meet. Providing a model for the formation of most of the bones in the body.

Types of Cartilage The human body has three types of cartilage: Hyaline cartilage Fibrocartilage Elastic cartilage

Functions of Bone Bones are composed of all tissue types. Their primary component is osseous connective tissue. The matrix is sturdy and rigid due to calcification, or mineralization.

Support and Protection Bones provide structural support and serve as a framework for the entire body. Bones also protect many delicate tissues and organs from injury and trauma.

Movement Muscles attached to the bones of the skeleton contract and exert a pull on the skeleton, which then functions as a series of levers.

Hemopoiesis Blood cell production in red bone marrow, which is located in some spongy bone. Red bone marrow contains stem cells that form all of the blood cell types.

Storage of Mineral and Energy Reserves More than 90% of the body’s reserves of the minerals calcium and phosphate are stored and released by bone. Calcium is an essential mineral for such body functions as muscle contraction, blood clotting, and nerve impulse transmission. Phosphate is needed for ATP utilization, among other things.

Classification of Bone by Shape Long Short Flat Irregular

Four Types of Bone Cells Osteoprogenitor cells stem cells derived from mesenchyme which produce other stem cells and osteoblasts Osteoblasts produce new bone, and onceosteoblasts become entrapped in the matrix they produce and secrete, they differentiate into osteocytes Osteocytes mature bone cells Osteoclasts are involved in bone resorption

Flat Bones Within the Skull Composed of two layers of compact bone, with a region of spongy bone sandwiched between them. Both layers of compact bone are covered by periosteum

Ossification Begins in the embryo and continues as the skeleton grows during childhood and adolescence. Even after the adult bones have formed, ossification continues. By the eighth through twelfth weeks of embryonic development, the skeleton begins forming from either thickened condensations of mesenchyme or a hyaline cartilage model of bone. These models are replaced by hard bone.

Intramembranous Ossification Produces the flat bones of the skull, some of the facial bones (zygomatic bone, maxilla), the mandible (lower jaw), and the central part of the clavicle (collarbone). It begins when mesenchyme becomes thickened and condensed with a dense supply of blood capillaries, and continues in several steps.

Endochondral Ossification Begins with a hyaline cartilage model and produces most of the other bones of the skeleton, including the bones of the upper and lower limbs, the pelvis, the vertebrae, and the ends of the clavicle.

Epiphyseal Line Formation Endochondral ossification of a long bone occurs in progressive stages. Bone growth is complete when each epiphyseal plate has ossified and the epiphyseal line has formed. Depending on the bone, epiphyseal plate ossification occurs between the ages of 10 and 25 years.

Bone Remodeling Although adult bone size has been reached, the bone continues to reshape itself throughout a person’s lifetime in a constant process of bone resorption and deposition.

Bone Growth Interstitial growth occurs in the epiphyseal plate as chondrocytes undergo mitosis Appositional growth occurs within the periosteum.

Bone Remodeling The continual deposition of new bone tissue and the removal (resorption) of old bone tissue. helps maintain calcium and phosphate levels in body fluids, and can be stimulated by stress on a bone occurs at both the periosteal and endosteal surfaces of a bone

Blood Supply and Innervation Bone is highly vascularized, especially in regions containing red bone marrow. Blood vessels enter bones from the periosteum. The nutrient artery and the nutrient vein supply the diaphysis of a long bone.

Effects of Hormones Control and regulate growth patterns in bone by altering the rates of both osteoblast and osteoclast activity. Growth hormone affects bone growth by stimulating the formation of another hormone, somatomedin which is produced by the liver. Somatomedin directly stimulates growth of cartilage in the epiphyseal plate.

Effects of Hormones Thyroid hormone stimulates bone growth. Growth hormone and thyroid hormone regulate and maintain normal activity at the epiphyseal plates until puberty. Calcitonin inhibits osteoclast activity.